/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.security.web.access;

import java.io.IOException;
import java.util.LinkedHashMap;
import java.util.Map.Entry;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.security.access.AccessDeniedException;
import org.springframework.util.Assert;

/**
 * An {@link AccessDeniedHandler} that delegates to other
 * {@link AccessDeniedHandler} instances based upon the type of
 * {@link AccessDeniedException} passed into
 * {@link #handle(HttpServletRequest, HttpServletResponse, AccessDeniedException)}.
 *
 * @author Rob Winch
 * @since 3.2
 *
 */
public final class DelegatingAccessDeniedHandler implements AccessDeniedHandler {
    private final LinkedHashMap<Class<? extends AccessDeniedException>, AccessDeniedHandler> handlers;

    private final AccessDeniedHandler defaultHandler;

    /**
     * Creates a new instance
     *
     * @param handlers
     *            a map of the {@link AccessDeniedException} class to the
     *            {@link AccessDeniedHandler} that should be used. Each is
     *            considered in the order they are specified and only the first
     *            {@link AccessDeniedHandler} is ued.
     * @param defaultHandler
     *            the default {@link AccessDeniedHandler} that should be used if
     *            none of the handlers matches.
     */
    public DelegatingAccessDeniedHandler(
            LinkedHashMap<Class<? extends AccessDeniedException>, AccessDeniedHandler> handlers,
            AccessDeniedHandler defaultHandler) {
        Assert.notEmpty(handlers, "handlers cannot be null or empty");
        Assert.notNull(defaultHandler, "defaultHandler cannot be null");
        this.handlers = handlers;
        this.defaultHandler = defaultHandler;
    }


    public void handle(HttpServletRequest request,
            HttpServletResponse response,
            AccessDeniedException accessDeniedException) throws IOException,
            ServletException {
        for(Entry<Class<? extends AccessDeniedException>, AccessDeniedHandler>  entry : handlers.entrySet()) {
            Class<? extends AccessDeniedException> handlerClass = entry.getKey();
            if(handlerClass.isAssignableFrom(accessDeniedException.getClass())) {
                AccessDeniedHandler handler = entry.getValue();
                handler.handle(request, response, accessDeniedException);
                return;
            }
        }
        defaultHandler.handle(request, response, accessDeniedException);
    }

}
